Cell cultures of neuronal tissue provide many advantages and opportunities for biochemical studies of the nervous system. We seek to exploit one system-cell cultures of sympathetic neurons-from this point of view. In this proposal, we have identified and will study three major problems for which both biochemical tools and cell culture techniques are available. These are: (1) The use of the snake venom protein alpha-bungarotoxin to probe neuronal acetylcholine receptors. We propose, in cultures of sympathetic neurons, to study the turnover, migration, and development of neuronal acetylcholine receptors as well as to study the effects of synapse formation on their post-synaptic properties (eg. distribution, concentration). We shall also determine the rate of development of these receptors during embryogenesis. (2) Nerve growth factor (NGF) receptor properties and mechanism of action. NGF has profound effects on sympathetic neurons both in vivo and in vitro. We shall use (I125)-NGF to determine the cellular target for NGF in culture; the distribution, number, and concentration of NGF receptors on the target cells, and the development of NGF receptors in vivo. We shall also seek to uncover the primary mode of action of NGF by studying the ability of various chemical substances to mimic, enhance, or inhibit the effect of NGF on cultured sympathetic neurons. (3) Creation and characterization of dividing cell lines with neuronal properties. We shall use somatic cell hybridization and suitable selection techniques to fuse primary sympathetic neurons with mouse neuroblastoma cells with the aim of creating dividing lines of cells with neuronal properties. Existing and new cell lines generated in this manner will be screened for the presence of various properties of sympathetic neurons (e.g. the ability to synthesize, store, or take-up catecholamines; sensitivity to NGF or chemical transmitters).